spring boot(10)-tomcat jdbc连接池

默认连接池

tomcat jdbc是从tomcat7开始推出的一个连接池，相比老的dbcp连接池要优秀很多。spring boot将tomcat jdbc作为默认的连接池，只要在pom.xml中引入了spring boot 的jdbc组件，就会自动引入tomcat jdbc连接池。关于引入jdbc和数据库的连接配置，参考第六篇

默认参数

以下是org.apache.tomcat.jdbc.pool.PoolProperties源码，这是tomcat jdbc连接池的默认初始参数。

这个类实现了一个接口PoolConfiguration，查看这个接口的源码，里面有每一个参数的详细说明。

官方文档： http://tomcat.apache.org/tomcat-8.5-doc/jdbc-pool.html 

public class PoolProperties implements PoolConfiguration, Cloneable, Serializable {

    private static final long serialVersionUID = -8519283440854213745L;
    private static final Log log = LogFactory.getLog(PoolProperties.class);

    public static final int DEFAULT_MAX_ACTIVE = 100;

    protected static final AtomicInteger poolCounter = new AtomicInteger(0);
    private volatile Properties dbProperties = new Properties();
    private volatile String url = null;
    private volatile String driverClassName = null;
    private volatile Boolean defaultAutoCommit = null;
    private volatile Boolean defaultReadOnly = null;
    private volatile int defaultTransactionIsolation = DataSourceFactory.UNKNOWN_TRANSACTIONISOLATION;
    private volatile String defaultCatalog = null;
    private volatile String connectionProperties;
    private volatile int initialSize = 10;
    private volatile int maxActive = DEFAULT_MAX_ACTIVE;
    private volatile int maxIdle = maxActive;
    private volatile int minIdle = initialSize;
    private volatile int maxWait = 30000;
    private volatile String validationQuery;
    private volatile int validationQueryTimeout = -1;
    private volatile String validatorClassName;
    private volatile Validator validator;
    private volatile boolean testOnBorrow = false;
    private volatile boolean testOnReturn = false;
    private volatile boolean testWhileIdle = false;
    private volatile int timeBetweenEvictionRunsMillis = 5000;
    private volatile int numTestsPerEvictionRun;
    private volatile int minEvictableIdleTimeMillis = 60000;
    private volatile boolean accessToUnderlyingConnectionAllowed = true;
    private volatile boolean removeAbandoned = false;
    private volatile int removeAbandonedTimeout = 60;
    private volatile boolean logAbandoned = false;
    private volatile String name = "Tomcat Connection Pool["+(poolCounter.addAndGet(1))+"-"+System.identityHashCode(PoolProperties.class)+"]";
    private volatile String password;
    private volatile String username;
    private volatile long validationInterval = 3000;
    private volatile boolean jmxEnabled = true;
    private volatile String initSQL;
    private volatile boolean testOnConnect =false;
    private volatile String jdbcInterceptors=null;
    private volatile boolean fairQueue = true;
    private volatile boolean useEquals = true;
    private volatile int abandonWhenPercentageFull = 0;
    private volatile long maxAge = 0;
    private volatile boolean useLock = false;
    private volatile InterceptorDefinition[] interceptors = null;
    private volatile int suspectTimeout = 0;
    private volatile Object dataSource = null;
    private volatile String dataSourceJNDI = null;
    private volatile boolean alternateUsernameAllowed = false;
    private volatile boolean commitOnReturn = false;
    private volatile boolean rollbackOnReturn = false;
    private volatile boolean useDisposableConnectionFacade = true;
    private volatile boolean logValidationErrors = false;
    private volatile boolean propagateInterruptState = false;
    private volatile boolean ignoreExceptionOnPreLoad = false;
    private volatile boolean useStatementFacade = true;

自定义参数

如果要修改某个默认参数值，可以在application.properties中配置，如下

spring.datasource.tomcat是前缀，maxActive是参数名，105是参数值，其他 参数格式也是一样

spring.datasource.tomcat.maxActive=105

在JAVA中自定义参数

在properties中自定义参数有一个问题，如果参数名写错了，是不会有任何错误提示的，会继续使用默认值 。在JAVA中配置可以避免这个问题，以下是设置maxActive参数，set其他参数也是一样

	@Bean
	public DataSource dataSource() {
		PoolProperties poolProperties = new PoolProperties();
		poolProperties.setMaxActive(105);
		return new DataSource(poolProperties);
	}

HikariCP

HikariCP是目前号称最好的连接池，没有之一。不过tomcat连接池有tomcat做为其后盾保障， 文档资料齐全，也更加持久稳妥。这里不讲解 HikariCP，有兴趣可访问https://github.com/brettwooldridge/HikariCP